Electromechanical actuators for primary flight control surfaces in aircraft, such as large commercial aircraft, include complex mechanical couplings in order to provide redundancy. These couplings are heavy and introduce additional failure modes and complex critical assembly tolerance constraints. Typically systems use speed summing of two independent motors. This requires that each motor has a brake and is connected to a differential which allows one motor to drive the load and, under a failure condition, to have its brake applied to allow the other motor to operate. This is a complex mechanical system that includes multiple gear meshes and bearing supports. This precision machine may have lower efficiency reducing the system performance. The brake is additionally a potential failure point and reduces the reliability of the system.
An electric motor controlled actuator which does not require motor redundancy, speed summing or brake systems to operate in a failure tolerant mode is desirable. Additionally, increasing the torque of the electric motor without increasing the current applied to each stator core element is also desirable.